What is a Written Scheme?
A Written Scheme of Examination (WSE), is a legal document required prior to use of Pressure Systems. This is legislated by UK regulations detailed in Pressure System Safety Regulations (PSSR) 2000. It details items within a Pressure System that necessitate examination by a competent person.
The aim of these Regulations is to prevent serious injury from the hazard of stored energy as a result of the failure of a pressure system or one of its component parts.
Before using any qualifying pressure equipment (new or otherwise), a written scheme of examination (WSE) must be in place, and an examination undertaken.
What is involved to prepare a Written Scheme?
The Competent Person will identify which items of the pressure system fall within the scope of the WSE, such as pressure vessel, protective devices and pipework. Once these items have been established the frequency of examinations will be outlined.
The following types of pressurised systems are likely to require a WSE:
- Compressed air systems where the vessel has a pressure volume product greater than 250 bar litres (This is calculated by multiplying the operating pressure of the vessel in bars by the size of the vessel in litres – bars x litres )
- Steam sterilisation autoclaves
- Coffee machines with steam boilers
- Rigid vessels over 250 bar litre, this includes expansion vessels and separators
- Pressure cookers
- Gas-loaded hydraulic accumulators, if forming part of a pressure system
- Portable hot water/steam-cleaning unit fitted with a pressure vessel
- Steam boilers, including standard or narrow-gauge steam locomotives
- Protective devices such as pressure gauges, safety valves, pipework, level indicators,
pressure and temperature switches
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